Various methods for treating corneal diseases such as keratoconus and glaucoma are known.
Keratoconus is a bilateral degenerative disorder of the eye that progressively thins and distorts the cornea, changing it to a more conical shape than its normal curvature. The cornea of the eye becomes thinner with a consequent reduction in rigidity and stability. This typically leads to substantial visual impairment and corneal scarring. In most cases, corrective lenses are effective to allow a patient to function normally. Under the influence of the internal pressure of the eye, weakening of the cornea leads to the eye bulging outward which in turn leads to the eye becoming ametropic. There is considerable risk of the ametropia becoming more severe if the disease is not treated effectively. However, further progression of the disease may require treatments such as the insertion of intrastromal corneal ring segments, corneal collagen cross-linking or corneal transplantation.
It has been found that a cross-linking of the collagen fibres of the cornea may increase the rigidity of the cornea such that the cornea may better resist the internal pressure on the eye. For this purpose, it is known to use a photo-sensitizer such as riboflavin or a riboflavin solution which is applied onto the eye. Such a photo-sensitizer is able, under the influence of photons, to chemically react with the corneal tissue. After the riboflavin has been absorbed by the eye, the eye is exposed to an irradiation with ultraviolet (UV) radiation. Under the influence of the UV radiation, the photo-sensitizer induces a cross-linking of the collagen fibres, thereby increasing the biomechanical rigidity of the cornea such that the cornea is likely to deform less under the influence of the pressure of the eye.
Glaucoma is a disorder of the eye wherein the optic nerve is damaged causing a loss of visual field. Raised intraocular pressure is a risk factor for developing glaucoma. The treatments for glaucoma include the use of medication such as eye drops for reducing intraocular pressure and both laser and conventional surgery.
Any reference herein to a “photo-sensitizer” must be interpreted to mean a reference to a substance which under the influence of photons, is able to chemically react with corneal tissue absorbing the photo-sensitizer so as to cross-link corneal collagen and thereby increase the rigidity of the corneal tissue.